因为m^2=n+2,n^2=m+2所以m^2-n^2=（n+4）-(m+4)=n-m即(m-n)(m+n)=-(m-n)m+n=-1m^3-2mn+n^3=m·m^2-2mn+n·n^2=(n+2)m-2mn+(m+2)n=mn+2m-2mn+mn+2n=2(m+n)因为m+n=-1所以m^3-2mn+n^3=-2
